This invention relates to a pointing device including a computer mouse pad.
A computer mouse is widely used as a pointing device for a personal computer, for controlling movement of a cursor over the display screen of the computer""s monitor. The common form of computer mouse has a mouse body for gripping in the user""s hand, the mouse body having a bottom wall which slides over a mouse pad. The bottom wall of the mouse body is formed with an opening which affords access to a cavity containing a mouse ball and a movement encoding mechanism. The mouse ball typically has a diameter of about {fraction (13/16)} inch. A retainer plate formed with a circular hole is fitted removably in the opening in the bottom wall of the mouse body. The diameter of the circular hole in the retainer plate is somewhat smaller than the diameter of the mouse ball, so the mouse ball is held captive in the cavity in the mouse body but protrudes through the hole in the retainer plate. As the user slides the mouse over the mouse pad, the mouse ball rolls against the movement encoding mechanism, which detects the rolling movement of the mouse ball and generates an electrical pulse signal in response thereto. The pulse signal is supplied to the computer""s system unit and is used by the system unit to control movement of the cursor over the computer""s monitor screen.
The computers that are used in schools are frequently equipped with mouses. If foreign matter, such as a dust particle, is present on the surface on which the mouse runs, such as a mouse pad, it might adhere to the mouse ball when the mouse moves over the particle. In this event, it is likely that the particle will be carried by the mouse ball into the cavity of the mouse body and be transferred to the movement encoding mechanism. There is then a possibility that operation of the movement encoding mechanism will be impaired. This may lead to erratic movement of the cursor. Although efforts are made to keep school computer labs clean, the computer mouse is frequently in need of cleaning to remove dirt from the ball and from the movement encoding mechanism.
A typical mouse pad is made of a resilient material, such as rubber. The upper surface of the mouse pad, on which the mouse slides, is smooth except for a layer of fabric which is glued to the upper surface of the mouse pad in order to provide frictional engagement with the mouse ball. Frequently, when a mouse that has been used on this type of mouse pad is cleaned, threads from the fabric layer of the mouse pad are found. It is likely that these threads are at least partly responsible for malfunction of the mouse.
In accordance with the invention there is provided a pointing device comprising a mouse having a mouse ball, and a mouse pad having a lower surface for resting on a support structure and an upper surface for supporting the mouse, the upper surface of the mouse pad being formed with grooves that are large enough that dust particles will fall into the grooves and will not adhere to the mouse ball when the mouse is moved over the mouse pad, the grooves being of width substantially smaller than the diameter of the mouse ball and being spaced at a distance substantially greater than the width of the grooves so that the mouse ball rolls smoothly over the mouse pad.